Instant cereal porridges, which are packaged as dry cereal flakes and which are readily reconstitutable upon the addition of water or milk to yield a cereal porridge having a "cooked" texture, have become increasingly popular with consumers. Instant porridges are favored by consumers because the amount of preparation and cleanup required to prepare conventional hot cereal porridges is considered burdensome. Thus, "instant" preparation of a porridge which requires merely the addition of water or milk directly to dried cereal flakes or beads to rehydrate and reconstitute the flakes or beads, alleviates most of the deterrent aspects of porridge preparation.
U.S. Pat. No. 2,999,018 issued to G. W. Huffman et al. discloses an instant rolled oatmeal cereal porridge. In accordance with the Huffman et al. patent the "instant cooked" character is provided to the rolled oats by the addition of an edible polysaccharide gum in sufficient amount to produce a cooked flavor and texture but insufficient to produce a pasty texture upon the addition of water. The addition of the edible polysaccharide gum to the oat flakes provides a gelatinized "cooked" quality uniformly to the cereal without actual gelatinization of the oat starches.
While addition of the polysaccharide gum is satisfactory for the purposes of adult feeding, it is not suitable for the preparation of an instant baby cereal porridge. It is essential for infant digestion, that the cereal grains or flours contained within a baby cereal be completely gelatinized prior to ingestion by the infant. Conventional preparation of a non-enzyme-containing, baby cereal involves a time-consuming in-home cooking step to assure that all the starch is completely gelatinized, prior to feeding of the infant. Therefore, a completely pregelatinized cereal porridge suitable for infant feeding, in which the "cooked" quality is apparent immediately upon rehydration of the dry cereal product with milk or water, is desirable from a consumer viewpoint. However, it is essential that such an instant cereal contain only flour starches which have been completely gelatinized prior to the drying and packaging thereof.
When cereal flour-water slurries are gelatinized the gelatinization process results in an increase in the viscosity of the cereal flour-water mixture. The increase of viscosity adds to the difficulty in further processing of the gelatinized mixture, particularly with regard to the drying of the mixture by drum drying.
Heretofore, treatment of the gelatinized mixture with enzymes has been a preferred method for reducing the viscosity of the gelatinized cereal mixture. Treatment with the enzyme reduces the viscosity of the gelatinized mixture by breaking down the cereal starch molecules, thereby decreasing the average molecular weight of the gelatinized starch molecules. However, enzyme treatment, in reducing the molecular weight of the starches, commonly result in sufficiently high glucose levels that upon drum drying, or upon the use of other highly efficient industrial drying methods, the dried product has an off-color due to browning reactions between the cereal proteins and the glucose, and also results in flake product densities which are too high for conventional product usage. Additionally, the enzyme treatment commonly decreases the viscosity of the reconstituted cereal porridge, yielding a "watery" porridge, and in extreme cases yielding a "porridge" which is merely a suspension of cereal in water or milk and in which the dry product tends to settle out of the water or milk during the rehydration process. For the reasons stated earlier, the enzyme treatment results in a darkening of the final dehydrated cereal product as well as of the reconstituted porridge made therefrom (particularly when the cereal flour contains oats).
Instant cereal porridge products intended for baby food use desirably must be superior in appearance when compared to conventionally prepared adult porridges in order to meet most consumers expectations. Darker color cereal products are generally perceived by the consumer as unappealing. Thus a darker color product is undesirable from both a consumer and marketing viewpoint. Bleaches and acids can be employed to lighten the color of the final instant porridge product, however, these chemical additives tend to degrade the protein contained in the cereal flours. Additionally, bleach and acid additives produce off-flavor notes, such as a rancid flavor or an "acid-bite". Processing of a cereal product by addition of an enzyme, bleach, or acid additives can be both costly and time-consuming. Moreover, consumer resistance to the addition of such not-found-in-nature additives to natural foods is becoming increasingly strong and the use of such additives, unless there is no reasonable natural alternative, is to be avoided.
However, some means to reduce the viscosity (and thus increase the fluidity) of the gelatinized cereal flour-water mixture is necessary to facilitate further processing and handling of the gelatinized mixture by drum drying or other drying methods. Uniformly drying of a gelatinized cereal flour-water mixture by drum drying in an efficient, industrially acceptable process requires an even coating of the drum by the cereal-water mixtures. Highly viscous gelatinized cereal flour-water mixtures are generally regarded as unsuited to drum dry techniques because they do not provide an even coating on the drums. Thus, a drastic reduction in viscosity from the peak gelatinization viscosity is necessary to provide the fluidity of the mixture which is essential for an even, uniform coating on the drum dryer. The drum drier capacity and efficiency will also be improved because the heat transfer is increased when the viscosity is lower.
The addition of oat flour to a baby cereal porridge is advantageous because oats have the highest protein content of any grain. And yet, this advantage makes oat flour particularly susceptible to browning reactions when processed in the presence of sugars. Nonetheless, the protein content of the porridge product can be enhanced by the addition of oats to the product. For instance, the protein content of a cereal product can be raised approximately 2-4% higher than the conventional porridges currently available to the consumer by the addition of a substantial amount of oat flour. Typical cereal porridge products which do not contain oat flour have a protein content in the range 8-11% protein based on the weight of the product. In accordance with a preferred process of the present invention, in which a substantial level of oat flour is employed as an ingredient, the protein level of the resulting dry product is approximately 12-14% protein based on the weight of the final dried product.
When oat flour is employed as one of the cereal flours, enzyme treatment (not in accordance with this invention), intensifies the dark color of the flake product and the porridge made therefrom. Bleaching or acid treatment of the dark oat-containing cereal product is disadvantageous because (a) it degrades the protein contained in the oats, and (b) it produces off-flavors, and (c) for the other reasons stated above.
A 1964 U.S. Pat. No. 3,133,818 issued to Gould et al discloses a process for precooking a substantially water-insoluble farinaceous product in which the farinaceous particles consisting of finely divided, highly dispersed particles of dry flour are "fluidized by contact with steam gas." The resulting "precooked" product (i.e. product which contacted heat source steam gas for period of about 2 to 200 seconds), prior to drying, has a moisture content in the range 15 to 50% by weight wet basis. There is no teaching or suggestion in the Gould patent of a process for mechanically imparting shear to a completely gelatinized, high moisture (greater than 70%) cereal flour-water mixture to reduce the viscosity of the mixture.